Convert a STL mesh object outline to a path (to trace the outline of an STL)
I found a workaround which may help others where grease pencil isn't needed but can be used if they want to.  Note: To use Grease Pencil Convert To Path it needs to be in 2D
2D slice (Good for copying threads from STL's to 3D print and if you want to use Grease Pencil - Convert to Path)
-Center Object pivot point and / STL to Origin 
-Apply scale and Location object transform on STL / Object
-Create Mesh Plane (larger than object)
-Select Plane - Add Boolean Modifier 
    Options - Intersect
    Object  - STL or Object
    Solver  - Fast

-Hide STL / Object (allows to see 2D section)

Extra: Can Select Plane and do a G - Z to see sections
Extra Extra: Can do in Geometry Nodes


3D slice (to view internals)
-Same as 2D Slice but change Solver to - Exact